Pneumatic guns use a compressed fluid, usually air or CO2, to propel a projectile down the barrel of the gun. Pneumatic guns come in many shapes and sizes. Some pneumatic guns are “pump style,” requiring the user to use lever force to input and compress ambient air. Others use compressed fluid tanks or cartridges that are mated with the gun, wherein the compressed fluid is transferred from the tank to the gun. For example, a Powerlet cartridge is a small disposable metal container holding 12 grams of liquid CO2 and often a small quantity of oil, used as a power source for certain air guns, paintball markers, and a few airsoft guns. Originally developed by Crossman Corporation and introduced to the market in 1954, the Powerlet CO2 cartridge has become the dominant source of power for inexpensive, rapid fire air guns from many manufacturers. The Powerlet container typically lasts between 20 and 40 shots depending on the gun and environmental conditions. You normally get about 10 average shots from a new bottle, then every shot after that becomes less powerful. Today, for paintball markers, this technology is considered outdated. Modern CO2 guns may still use the Powerlet, but also use a variety of fluid tanks containing CO2 and other fluids in various shapes and sizes. For example, many paint ball guns currently use a 12 oz or 20 oz aluminum CO2 tank can. The 12 g Powerlet cartridge is still favored for paintball and bb pistols, and offer considerable weight savings over a modern high pressure air tank.